Financial experts say the terrorist strikes in the US constitute the single most expensive man-made disaster in history.

Insurance firms face claims of about $15bn (£10.2bn) associated with the economic and human costs of the attacks, sector specialists have said.

Some estimates put the cost as high as $25-30bn.

Until Tuesday, the most expensive isolated catastrophe unassociated with natural disasters had been the 1988 Piper Alpha oil platform blast off the British coast, over which insurers paid out $3bn.

But this sum is dwarfed by the payouts following earthquakes hurricanes or storms.

The cost of Hurricane Andrew in 1992 would, in 2001 terms, come to $22-25bn, a City analyst told BBC News Online.

Claims breakdown

Organisations publishing early forecasts of the costs of Tuesday's terror attacks include rating agency Moody's, which has given a range of $10bn-15bn.

Top insurance disasters

1: Hurricane Andrew, 1992, $19.7bn

2: Los Angeles earthquake, 1994, $16.3bn

3: Cyclone Mireille, 1991, $7.14bn

4: Storm Daria, 1990, $6.05bn

5: Storms Lothar and Martin, 1999, $6.00bn

Source: Swiss Re
Costs at 2000 prices

While Moody's has failed to detail its estimate, a report from a leading City bank obtained by BBC News Online has put the damage to the World Trade Center itself at $4bn, although this may rise as costs to the Salomon Brothers offices and other neighbouring buildings are included.

In terms of aircraft, insurers face paying out up to $1bn, with $3bn allowed to cover claims over loss of business, and $2bn for claims involving loss of life.

Legal cases brought by relatives of those lost in the disaster could trigger a further $3bn in payouts, the bank estimated.

State contribution?

Losses will be shouldered by insurers throughout the world. Lloyd's of London, the world's biggest insurer, is estimated by industry observers to be facing claims of about £300m.

Insurers' claims estimates

Swiss Re: $1bn

Munich Re: 1bn euros

Zurich Financial: $400m

Among reinsurers, firms which take on risks laid off by front-line insurers, Swiss Re said the terrorist attacks would cost it about $1bn - roughly the same as the storms which ravaged Europe in 1999.

Munich Re has admitted it will suffer costs which are considerable, but insufficient to threaten its financial stability.

And Zurich Financial Services, in a statement late on Wednesday saying a few of its New York staff were missing, estimated pre-tax losses through the attacks of up to £400m.

"As a major US insurer and reinsure, it is our business to reimburse clients for their losses and we shall do so diligently," the firm said.

Some insurance chiefs believe the US government will shoulder much of the costs, following the lead of the French state, which paid out compensation to victims of terrorist attacks in 1985 and 1986.

Serge Osouf, director general of French insurance group Scor, said he could "imagine the American authorities stepping in".